#include <bits/stdc++.h>
using namespace std;

#define REP(i,n) for(int i=0;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<29
#define LINF LLONG_MAX/3
#define MP make_pair
#define PB push_back
#define EB emplace_back
#define ALL(v) (v).begin(),(v).end()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;

int N,M;
vector<int> A,B;
vector<vector<int>> G;
vector<set<int>> S;

int main(){
    cin>>N>>M;
    G.resize(N);
    S.resize(N);
    rep(i,M){
        int a,b;cin>>a>>b;
        a--,b--;
        A.PB(a);
        B.PB(b);
        G[a].PB(b);
        G[b].PB(a);
    }
    for(int u:G[0]){
        for(int v:G[u]){
            if(v==0 or u==0) continue;
            S[v].insert(u);
        }
    }

    rep(i,M){
        int a=A[i],b=B[i];
        if(a==b or a==0 or b==0) continue;
        for(int u1 : S[a]){
            for(int u2 : S[b]){
                if(u1!=0 and u1!=b and u2!=0 and u2!=a and u1!=u2){
                    cout << "YES" << endl;
                    return 0;
                }
            }
        }
    }
    cout << "NO" << endl;
}